In recent papers, we show how accretion disks around massive black holes could act as dynamos producing magnetic jets similar to the jets that create spheromaks in the laboratory. In this paper, we discuss how these magnetic astrophysical jets might naturally produce runaway ion beams accelerated to $10^{20}$  eV or more, finally ejected as ultra high energy cosmic rays (UHECRs) long regarded as one of the mysteries of astrophysics. The acceleration is mainly due to the drift cyclotron loss cone kinetic instability known from plasma research. Experiments and simulations are suggested to verify the acceleration process.

How large, 100-AU scale, rotationally supported disks form around protostars remains unsettled, both observationally and theoretically. In this contribution, we discuss the theoretical difficulties with disk formation in the presence of a dynamically significant magnetic field and their possible resolutions. These difficulties are caused by the concentration of magnetic field lines close to the forming star by protostellar collapse, and the strong magnetic braking associated with the concentrated field. Possible resolutions include magnetic field-rotation axis misalignment, non-ideal MHD effects, and turbulence. The field-rotation misalignment has been shown to promote disk formation, especially when the field is relatively weak and the misalignment angle is relatively large. Non-ideal MHD effects can enable the formation of small disks at early times. How such disks grow at later times remains to be fully quantified. Turbulence has been found to enable disk formation in a number of simulations, but the exact reason for its beneficial effect is debated.

We interpret the radio/X-ray correlation of LR ∝ LX~1.4 for LX/LEdd ≳ 10−3 with a detailed disk corona-jet model, in which the accretion flow and the jet are connected by a parameter, η, describing the fraction of the matter in the accretion flow ejected outward to form the jet. We calculate LR and LX at different Ṁ, adjusting η to fit the observed radio/X-ray correlation of the black hole X-ray transient H1743-322 for LX/LEdd > 10−3. It is found that the value of η for this radio/X-ray correlation for LX/LEdd > 10−3, is systematically less than that of the case for LX/LEdd < 10−3, which is consistent with the general idea that the jet is often relatively suppressed at the high luminosity phase in black hole X-ray binaries.

From the extreme position of disk motion, we infer the neutron star (NS) surface magnetic field strength (B0) of Z-source GX 17+2 and Cyg X-2. The inferred B0 of GX 17+2 and Cyg X-2 are ~(1–5)×108 G and ~(1–3)×108 G, respectively, which are not inferior to that of millisecond X-ray pulsars or atoll sources. It is likely that the NS magnetic axis of Z sources is parallel to the axis of rotation, which could result in the lack of pulsations in these sources.

We explore conditions and structure of accretion disks in the short-period Cataclysmic Variables, which have evolved beyond the period minimum. We show that the accretion disk in a system with extreme mass ratio grows in the size reaching 2:1 resonance radius and are relatively cool. They also become largely optically thin in the continuum, contributing to the total flux less than the stellar components of the system. In contrast, the viscosity and the temperature in spiral arms formed at the outer edge of the disk are higher and their contribution in continuum plays an increasingly important role. We model such disks and generate light curves which successfully simulate the observed double-humped light curves in the quiescence.

During the quiescent phases, the spectra of cataclysmic variables are studied. We model the fluxes by means of the photoionization code CLOUDY, and in the model it is assumed that the geometry of disks is cylindrical. Using this method, we input a series of reasonable parameters and get a spectral library.

Using RXTE observations, we investigate the evolution of inner disk radius (Rin) of Cir X-1 during two cycles and find obvious orbital modulation. We argue that the modulation is attributed to its high orbital eccentricity. The disk luminosity is inversely with the inner disk temperature (kTin), which is ascribed to the slow increase of kTin and, however, the rapid decrease of Rin during the passage for the neutron star to depart from the companion star.

We propose that a magnetar could be formed during the core collapse of massive stars or coalescence of two normal neutron stars, through collecting and inheriting the magnetic fields magnified by hyperaccreting disk. After the magnetar is born, its dipole magnetic fields in turn have a major influence on the following accretion. The decay of its toroidal field can fuel the persistent X-ray luminosity of either an SGR or AXP; however the decay of only the poloidal field is insufficient to do so.

We describe the results of our numerical simulations of the collapse of a massive stellar core to a BH, performed in the framework of full general relativity incorporating finite-temperature equation of state and neutrino cooling. We adopt a 100 M⊙ presupernova model calculated by Umeda & Nomoto (2008), which has a massive core with a high value of entropy per baryon. Changing the degree of rotation for the initial condition, we clarify the dependence of the outcome on this. When the rotation is rapid enough, the shock wave formed at the core bounce is deformed to be a torus-like shape. Then, the infalling matter is accumulated in the central region due to the oblique shock at the torus surface, hitting the hypermassive neutron star (HMNS) and dissipating the kinetic energy there. As a result, outflows can be launched. The HMNS eventually collapses to a BH and an accretion torus is formed around it. We also found that the evolution of the BH and torus depends strongly on the rotation initially given.

We studied the structure of the H2O super maser region in Orion with VLBI angular resolution of 0.1 mas or 0.05 AU. The maser emission (F ∼ 8 MJy) was determined by highly organized structure: accretion disk, bipolar outflow, torus and surrounding shell. The accretion disk, divided into protoplanetary rings, is viewed edge-on. The disk rotates as a rigid body with velocities V ∼ ΩR and the rotation period is ∼ 170 yrs. The highly collimated bipolar outflow has a size of 9×0.7 AU, a velocity of ∼ 10 km/s. In the center a bright compact (≤0.05 AU) source – ejector is located, surrounded by a torus 0.6 AU in diameter. The outflow has a helix structure, which is determined by precession with a period of T ∼ 10 yrs. Comet-like bullets were observed on distances up to 80 AU.

The conventional picture of disk accretion onto magnetized neutron stars has been challenged by the spin changes observed in a few X-ray pulsars, and by theoretical results from numerical simulations of disk-magnetized star interactions. Here we present a model for the torque exerted by accretion disks on magnetized neutron stars, assuming accretion continues even for fast rotators.

Spectral observations of the WN3p star WR46 (HD 104994) obtained during June 1993 and January/February 1994 display large amplitude radial velocity variations of the strong emission lines Nv 4603-19Å and HeII 4686A, on a time scale of a fraction of a day. The most probable period found is 0.311 d, similar to the photometric period found by previous authors. The amplitude of the radial velocity variations of Nv emission is almost twice that of HeII. Noting the similarity of WR46 with low mass X-ray binaries, we suggest that the emission line spectrum corresponds to that of a luminous accretion disk in an evolved binary system.

The structure and stability of the two-temperature accretion disk around compact object with central soft-photon source is studied.

We consider two forms of variability in black hole accretion disks: harmonically oscillating modes trapped near the disk inner edge, and noisy fluctuations throughout the entire disk. We apply the former to AGN disks, and the latter to the X-ray power spectra of GX339-4.

This paper investigates the tidal effect on accretion disk in CVs and sets up a simplified model in which the secondary’s gravitation is substituted by a mean tidal torque. We find that a linear tidal torque will not be able to maintain an equilibrium disk. By using the result of the radius of the equilibrium disk approximately equals to the tidal radius, which was obtained by using the two dimensional numerical simulation invoking nonlinear tidal effect, we give the modified tidal dissipation function for our simplified model which could be used to interpret the outburst of the dwarf nova with tidal effect. The paper also shows that the radius of an equilibrium disk with a torus is slightly small than the Lubow-Shu radius, and the tidal effect may also cause the cycle of quiescence-superoutburst in addition to the cycle of quiescence-outbursts-superoutburst.